The Histopathology Core will perform a vital function in Paul D. Weilstone MDCRC. The director of the core is an experienced muscle pathologist (Z. Sahenk, MD, Ph.D, Director of the Histopathology Laboratory at Nationwide Children's Hospital). Project 1 will require analysis of muscle tissue taken directly from DMD patients. In Aim 1 of Project 1, T cell infiltration will be examined as an expression of a pre-existing immune response to dystrophin. In addition, sequencing of the DMD mRNA will be performed, in order to assess the relationship between altered splicing and antigenic dystrophin epitopes. In Aim 2 of Project 1, specific T cell immunity will be studied before and after corticosteroid treatment. Aim 3 of Project 1 closely scrutinizes gene expression and immune response following AAV-micro-dystrophin delivery to muscle. In Project 2 emphasis switches to an experimental paradigm using the rhesus macaque. This too is familiar territory to this laboratory because tissue from this animal model has been processed in this laboratory for the past several years. In Aim 1 of project 1 AAV.micro-dystrophin gene delivery will be examined after depleting neutralizing antibodies to study the role of T cell immunity to viral capsid. In Aim 2 of project 2 tissue sections will be used to help define the role of CD4+ and CD8+ T cells against a foreign transgene product. In the final Aim 3 of Project 2 similar tissue studies will be necessary to understand the role of possible immunosuppressant agents. In the course of study of both human and non-human primate tissue, histologic sections will employ standard stains and immunohistochemistry for gene expression and Immunological markers for T cell subsets, and western blots similar to every day studies in this laboratory. The success of this proposal is dependent on the experience and excellence ofthis laboratory for the following reasons: 1) The mission of each Project will be facilitated by the expertise of a single laboratory with built in quality control measures to process all tissues in a consistent manner. 2) The objectivity of the results will be enhanced by separating the Pi's in Projects 1 and 2 from the outcome measures. 3) There will be greater consistency between each of the Projects by having all tissue sections processed by the same staff.